1. Field of the Invention
The present invention relates to footwear. More particularly, the present invention relates to a filter system that prevents water, other liquids, and particulates from obstructing the operation of components located within an article of footwear.
2. Description of Background Art
The principal objectives of modern athletic footwear design are to minimize weight while maximizing comfort, cushioning, stability, and durability. In order to meet this goal, footwear designers use a broad range of materials, shoe design techniques, and shoe making methods. The basic design of athletic footwear, however, remains largely uniform.
Typical athletic footwear includes two primary elements, an upper and a sole. Usually formed of leather, synthetic materials, or a combination thereof, the purpose of the upper is to comfortably secure the wearer's foot to the sole while providing necessary ventilation. Attached to the upper is the sole. The sole ordinarily has a multi-layer construction which includes an insole, midsole, and outsole. The insole commonly consists of a thin padded member placed within the upper to enhance shoe comfort. The midsole forms the middle layer of the sole and typically includes a resilient foam material that cushions the foot from the impact forces of running, walking, or other movement. The outsole is usually formed of a durable material, such as synthetic or natural rubber, to resist wear during use. In many cases, the outsole incorporates a textured surface to enhance traction.
An alternate midsole construction, disclosed in U.S. Pat. No. 4,183,156 (patented Jan. 15, 1980 to Marion F. Rudy), incorporated by reference, includes a midsole component in which cushioning is provided by a fluid-filled bladder formed of elastomeric materials. The bladder includes a plurality of tubular chambers which extend longitudinally through the length of an article of footwear. The various tubular chambers are in fluid communication and jointly extend across the width of the footwear. U.S. Pat. No. 4,219,945 (patented Sep. 2, 1980 to Marion F. Rudy), incorporated by reference, discloses a fluid-filled bladder encapsulated within a foam material. The combination of the bladder and the encapsulating foam material functions as a midsole. An upper may be cemented to the upper surface of the encapsulating foam material and an outsole may be affixed to the lower surface.
The fluid-filled bladders disclosed in the '156 and '945 patents utilize a gas with a large molecular size that cannot diffuse through the bladder walls. In contrast, other bladder devices, including the bladders disclosed in U.S. Pat. Nos. 4,912,861 (patented Apr. 3, 1990 to Ing-Chung Huang); U.S. Pat. No. 5,335,382 (patented Aug. 9, 1994 to Yin-Jun Huang); and U.S. Pat. No. 5,937,462 (patented Aug. 17, 1999 to Ing-Chung Huang), which are incorporated by reference, use ambient air as the inflation gas. Unlike a gas with a large molecular size, air diffuses through bladder walls. Accordingly, those bladders that use air as an inflation gas frequently include pumps or other inflation devices to inflate the bladder with air. In addition, such bladders include valves that prevent the air from escaping through the inlet.
Over time, water and a variety of particulates, including dust, dirt, small rocks, plants, cleaning solutions, oils, cosmetics, and paint, may enter bladders, pumps, and valves in systems that include ambient air inlets. The bladders, pumps, and valves may, therefore, develop particulate deposits or mold growths that detrimentally affect performance of the bladder pumping system or the valves that prevent air from escaping. Accordingly, the art requires an improved ambient air-filled bladder that prevents substantial amounts of liquids and particulates from entering the bladder and detrimentally affecting bladder performance.